Vulnerability-Lookup

FKIE_CVE-2026-39804

Vulnerability from fkie_nvd - Published: 2026-05-01 21:16 - Updated: 2026-05-05 19:37

Severity ?

8.2 (High) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Summary

Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion when WebSocket permessage-deflate compression is enabled. 'Elixir.Bandit.WebSocket.PerMessageDeflate':inflate/2 in lib/bandit/websocket/permessage_deflate.ex calls :zlib.inflate/2 with no output-size cap, then materializes the entire decompressed payload as a single binary via IO.iodata_to_binary/1. The websocket_options.max_frame_size option only bounds the on-the-wire (compressed) frame size, not the decompressed output. A high-ratio compressed frame (e.g. uniform data at ~1024:1 ratio) can stay well under any wire-size limit while forcing GiB-scale heap allocations in the connection process before any application code runs. An unauthenticated attacker who can open a WebSocket connection can send a single such frame to exhaust the BEAM node's memory and trigger an OOM kill. This vulnerability requires both Bandit's server-level websocket_options.compress and the per-upgrade compress: true option passed to WebSockAdapter.upgrade/4 to be enabled. Stock Phoenix and LiveView applications are not affected as they default to compress: false. This issue affects bandit: from 0.5.9 before 1.11.0.

References

	URL	Tags
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://cna.erlef.org/cves/CVE-2026-39804.html
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://github.com/mtrudel/bandit/commit/8156921a51e684a951221da7bc30a70a022f722e
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://github.com/mtrudel/bandit/security/advisories/GHSA-frh3-6pv6-rc8j
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://osv.dev/vulnerability/EEF-CVE-2026-39804
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/mtrudel/bandit/security/advisories/GHSA-frh3-6pv6-rc8j

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion when WebSocket permessage-deflate compression is enabled.\n\n\u0027Elixir.Bandit.WebSocket.PerMessageDeflate\u0027:inflate/2 in lib/bandit/websocket/permessage_deflate.ex calls :zlib.inflate/2 with no output-size cap, then materializes the entire decompressed payload as a single binary via IO.iodata_to_binary/1. The websocket_options.max_frame_size option only bounds the on-the-wire (compressed) frame size, not the decompressed output. A high-ratio compressed frame (e.g. uniform data at ~1024:1 ratio) can stay well under any wire-size limit while forcing GiB-scale heap allocations in the connection process before any application code runs.\n\nAn unauthenticated attacker who can open a WebSocket connection can send a single such frame to exhaust the BEAM node\u0027s memory and trigger an OOM kill.\n\nThis vulnerability requires both Bandit\u0027s server-level websocket_options.compress and the per-upgrade compress: true option passed to WebSockAdapter.upgrade/4 to be enabled. Stock Phoenix and LiveView applications are not affected as they default to compress: false.\n\nThis issue affects bandit: from 0.5.9 before 1.11.0."
    }
  ],
  "id": "CVE-2026-39804",
  "lastModified": "2026-05-05T19:37:28.367",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 8.2,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-05-01T21:16:16.853",
  "references": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://cna.erlef.org/cves/CVE-2026-39804.html"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/mtrudel/bandit/commit/8156921a51e684a951221da7bc30a70a022f722e"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-frh3-6pv6-rc8j"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-39804"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-frh3-6pv6-rc8j"
    }
  ],
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary"
    }
  ]
}

CVE-2026-39804 (GCVE-0-2026-39804)

Vulnerability from cvelistv5 – Published: 2026-05-01 20:34 – Updated: 2026-05-13 13:48

Title

WebSocket permessage-deflate inflate has no output-size cap in bandit

Summary

Severity ?

8.2 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

EEF

References

4 references

URL	Tags
https://github.com/mtrudel/bandit/security/adviso…	vendor-advisoryrelated
https://cna.erlef.org/cves/CVE-2026-39804.html	related
https://osv.dev/vulnerability/EEF-CVE-2026-39804	related
https://github.com/mtrudel/bandit/commit/8156921a…	patch

Impacted products

2 products

Vendor	Product	Version
mtrudel	bandit	Affected: 0.5.9 , < 1.11.0 (semver) cpe:2.3:a:mtrudel:bandit::::::::
mtrudel	bandit	Affected: da4027cff7d2b80319e76fe7a32f84beceec490a , < 8156921a51e684a951221da7bc30a70a022f722e (git) cpe:2.3:a:mtrudel:bandit::::::::

Credits

Peter Ullrich Mat Trudel Jonatan Männchen

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-39804",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-02T01:19:00.687361Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-02T01:19:55.677Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-frh3-6pv6-rc8j"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.Bandit.WebSocket.PerMessageDeflate\u0027"
          ],
          "packageName": "bandit",
          "packageURL": "pkg:hex/bandit",
          "product": "bandit",
          "programFiles": [
            "lib/bandit/websocket/permessage_deflate.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Bandit.WebSocket.PerMessageDeflate\u0027:inflate/2"
            }
          ],
          "repo": "https://github.com/mtrudel/bandit",
          "vendor": "mtrudel",
          "versions": [
            {
              "lessThan": "1.11.0",
              "status": "affected",
              "version": "0.5.9",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.Bandit.WebSocket.PerMessageDeflate\u0027"
          ],
          "packageName": "mtrudel/bandit",
          "packageURL": "pkg:github/mtrudel/bandit",
          "product": "bandit",
          "programFiles": [
            "lib/bandit/websocket/permessage_deflate.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Bandit.WebSocket.PerMessageDeflate\u0027:inflate/2"
            }
          ],
          "repo": "https://github.com/mtrudel/bandit",
          "vendor": "mtrudel",
          "versions": [
            {
              "lessThan": "8156921a51e684a951221da7bc30a70a022f722e",
              "status": "affected",
              "version": "da4027cff7d2b80319e76fe7a32f84beceec490a",
              "versionType": "git"
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "The vulnerability is only reachable when both of the following conditions are true:\u003cul\u003e\u003cli\u003eBandit\u0027s server-level \u003ctt\u003ewebsocket_options.compress\u003c/tt\u003e is enabled (it defaults to \u003ctt\u003etrue\u003c/tt\u003e).\u003c/li\u003e\u003cli\u003eThe per-upgrade \u003ctt\u003ecompress: true\u003c/tt\u003e option is passed to \u003ctt\u003eWebSockAdapter.upgrade/4\u003c/tt\u003e (it defaults to \u003ctt\u003efalse\u003c/tt\u003e; Phoenix\u0027s default is also \u003ctt\u003efalse\u003c/tt\u003e).\u003c/li\u003e\u003c/ul\u003eStock Phoenix and LiveView applications are not affected because \u003ctt\u003ecompress: false\u003c/tt\u003e is their default."
            }
          ],
          "value": "The vulnerability is only reachable when both of the following conditions are true:\n- Bandit\u0027s server-level websocket_options.compress is enabled (it defaults to true).\n- The per-upgrade compress: true option is passed to WebSockAdapter.upgrade/4 (it defaults to false; Phoenix\u0027s default is also false).\n\nStock Phoenix and LiveView applications are not affected because compress: false is their default."
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "1.11.0",
                  "versionStartIncluding": "0.5.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ],
          "operator": "AND"
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Peter Ullrich"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Mat Trudel"
        },
        {
          "lang": "en",
          "type": "analyst",
          "value": "Jonatan M\u00e4nnchen"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion when WebSocket permessage-deflate compression is enabled.\u003cp\u003e\u003ctt\u003e\u0027Elixir.Bandit.WebSocket.PerMessageDeflate\u0027:inflate/2\u003c/tt\u003e in \u003ctt\u003elib/bandit/websocket/permessage_deflate.ex\u003c/tt\u003e calls \u003ctt\u003e:zlib.inflate/2\u003c/tt\u003e with no output-size cap, then materializes the entire decompressed payload as a single binary via \u003ctt\u003eIO.iodata_to_binary/1\u003c/tt\u003e. The \u003ctt\u003ewebsocket_options.max_frame_size\u003c/tt\u003e option only bounds the on-the-wire (compressed) frame size, not the decompressed output. A high-ratio compressed frame (e.g. uniform data at ~1024:1 ratio) can stay well under any wire-size limit while forcing GiB-scale heap allocations in the connection process before any application code runs.\u003c/p\u003e\u003cp\u003eAn unauthenticated attacker who can open a WebSocket connection can send a single such frame to exhaust the BEAM node\u0027s memory and trigger an OOM kill.\u003c/p\u003e\u003cp\u003eThis vulnerability requires both Bandit\u0027s server-level \u003ctt\u003ewebsocket_options.compress\u003c/tt\u003e and the per-upgrade \u003ctt\u003ecompress: true\u003c/tt\u003e option passed to \u003ctt\u003eWebSockAdapter.upgrade/4\u003c/tt\u003e to be enabled. Stock Phoenix and LiveView applications are not affected as they default to \u003ctt\u003ecompress: false\u003c/tt\u003e.\u003c/p\u003e\u003cp\u003eThis issue affects bandit: from 0.5.9 before 1.11.0.\u003c/p\u003e"
            }
          ],
          "value": "Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion when WebSocket permessage-deflate compression is enabled.\n\n\u0027Elixir.Bandit.WebSocket.PerMessageDeflate\u0027:inflate/2 in lib/bandit/websocket/permessage_deflate.ex calls :zlib.inflate/2 with no output-size cap, then materializes the entire decompressed payload as a single binary via IO.iodata_to_binary/1. The websocket_options.max_frame_size option only bounds the on-the-wire (compressed) frame size, not the decompressed output. A high-ratio compressed frame (e.g. uniform data at ~1024:1 ratio) can stay well under any wire-size limit while forcing GiB-scale heap allocations in the connection process before any application code runs.\n\nAn unauthenticated attacker who can open a WebSocket connection can send a single such frame to exhaust the BEAM node\u0027s memory and trigger an OOM kill.\n\nThis vulnerability requires both Bandit\u0027s server-level websocket_options.compress and the per-upgrade compress: true option passed to WebSockAdapter.upgrade/4 to be enabled. Stock Phoenix and LiveView applications are not affected as they default to compress: false.\n\nThis issue affects bandit: from 0.5.9 before 1.11.0."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-130",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-130 Excessive Allocation"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 8.2,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-770",
              "description": "CWE-770 Allocation of Resources Without Limits or Throttling",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-13T13:48:07.878Z",
        "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "shortName": "EEF"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory",
            "related"
          ],
          "url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-frh3-6pv6-rc8j"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://cna.erlef.org/cves/CVE-2026-39804.html"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://osv.dev/vulnerability/EEF-CVE-2026-39804"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/mtrudel/bandit/commit/8156921a51e684a951221da7bc30a70a022f722e"
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "title": "WebSocket permessage-deflate inflate has no output-size cap in bandit",
      "workarounds": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "Do not pass \u003ctt\u003ecompress: true\u003c/tt\u003e to \u003ctt\u003eWebSockAdapter.upgrade/4\u003c/tt\u003e. Omitting this option (or setting it to \u003ctt\u003efalse\u003c/tt\u003e) prevents permessage-deflate from being negotiated, so the inflate path is never reached."
            }
          ],
          "value": "Do not pass compress: true to WebSockAdapter.upgrade/4. Omitting this option (or setting it to false) prevents permessage-deflate from being negotiated, so the inflate path is never reached."
        }
      ],
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
    "assignerShortName": "EEF",
    "cveId": "CVE-2026-39804",
    "datePublished": "2026-05-01T20:34:24.604Z",
    "dateReserved": "2026-04-07T12:28:54.916Z",
    "dateUpdated": "2026-05-13T13:48:07.878Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

FKIE_CVE-2026-39804

CVE-2026-39804 (GCVE-0-2026-39804)

Tags

Sightings

Nomenclature